Avoid positional arguments to define-minor-mode

[tarsius]

Back in Emacs-21.1, define-minor-mode grew keyword arguments to replace its old positional arguments. Starting with Emacs-28.1 warning will be omitted if positional arguments are still used.

Using nil as explicit dummy values for the optional arguments and then subsequently using the corresponding keyword arguments to set the proper was never necessary and also didn't make much sense.

[yyoncho]

Thank you!